Process for production of asphalt

ABSTRACT

A process is disclosed for improving the temperature-viscosity characteristics of asphalt by treating an asphalt-containing material with a solvent that contains at least 50% by volume of acetone and at least 1% by volume of a low-boiling liquid hydrocarbon, and recovering the asphalt with improved viscosity temperature characteristics as the raffinate phase.

United States Patent 1191 Dorman-Smith Dec. 31, 1974 [54] PROCESS FOR PRODUCTION OF ASPHALT 2,366,657 l/1945 Sorem 208/45 X 2,72, 0 I2 55 B ..2 [76] Inventor: Dmmamsmth, 7 Bushy 1873 1 1/i 59 xiii? 30 834 Park Rathgar, Dublin 6, Ireland 2,943,992 7/1960 Blisard 61 a1 208/34 x [22] Filed: Dec. 5, 1969 Primary Exanzinerloseph L. Schofer [21] Appl' 882742 Assistant Examiner-H. J. Lilling Attorney, Agent, or FirmGlen R. Grunewald; Harold [52] US. Cl 106/278, 106/271, 106/273, L. Denkler 208/34 [51] Int. Cl Cl0c 3/08, Cl0c1/18 [58] Field Of Search 106/273-285, [57] ABSTRACT 106/27O"271; 208/341 45 A process is disclosed for improving the temperatureviscosity characteristics of asphalt by treating an as- [56] References C'ted phalt-containing material with a solvent that contains UNITED STATES PATENTS at least 50% by volume of acetone and at least 1% by 1,674,710 6/1928 Wittek volume Of a low-boiling liquid hydrocarbon, and W 2,049,046 7/1936 Bray covering the asphalt with improved viscosity tempera- 2,08l,733 5/1937 Bray ture characteristics as the raftinate phase. 2,137,207 11/1938 Grahame et al. 208/34 2,337,448 12/1943 Carr 208/45 X 4 Claims, N0 Drawings I I PROCESS FOR PRODUCTION OF ASPHALT BACKGROUND OF THE INVENTION Asphalt is usually the residue portion of a hydrocarbon mixture, typically the residue of a crude petroleum oil that remains when other material is separated by distillation and vacuum flashing. Asphalt is a very complex high boiling hydrocarbon mixture and its composition is difficult to control and even difficult to analyze. However, asphalt can be separated into three classes of materials; oils, which are largely saturated; asphaltenes, which are largely high molecular weight condensed aromatic ring systems; and resins, which are aromatic and heterocyclic materials having aliphatic side chains.

The residues obtained by removing lower boiling hydrocarbons from crude are sometimes treated with low boiling aliphatic hydrocarbons to precipitate asphalt by processes known as solvent deasphalting. The pitch that results from such a process is not usually adequate for road-building because its temperature-viscosity characteristics are not adequate. To be useful for roadbuilding, an asphalt must have an acceptable viscosity over the temperature range that the road surface will be exposed to during use. Thus, to perform adequately an asphalt must not be too brittle in the winter or too soft in the summer.

Although residues and pitches that are too soft may be hardened by processes such as air blowing, and those that are too hard and brittle may be softened by blending less viscous material with them, asphalts with good temperature-viscosity characteristics are usually found rather than made; that is, they are simply recovered from crudes that have an asphalt fraction that has good road-building characteristics.

A measure of good viscosity-temperature characteristics of an asphalt is the flatness of the curve of viscosity vs. temperature for that asphalt. A curve with very flat slope indicates a desirable asphalt. Such curves, for convenience in use, are usually plotted as the log log of the viscosity vs. the log of the temperature.

THE INVENTION This invention involves a process for improving the temperature-viscosity characteristics of asphalt by solvent extraction of an asphalt-containing material with a special solvent. The special solvent employed in the process of this invention includes at least two compo nents. One is a low boiling liquid hydrocarbon which is capable of placing substantially all of the asphaltcontaining fraction in solution. This solubility characteristic defines the character of the solvent rather than the quantity; that is, the low-boiling liquid hydrocarbon is one that is capable of dissolving to a large extent the asphaltenes, the oils and the resins in a residue even though the solvent used is not in sufficient quantity to actually dissolve all of the asphalt. The other component of the solvent is acetone, which by itself is a virtual non-solvent at room temperature and for short contact times.

It has been found that the joint action of the solvent pair including at least 50% by volume of acetone and at least 1% by volume of low boiling liquid hydrocarbon selectively dissolves undesirable compounds from asphalt and leaves a lower layer phase with a lower viscosity-temperature sensitivity; that is, with a flatter viscosity vs. temperature curve. The process of the invention may be used to improve the viscositytemperature characteristics of an asphalt, and it may also be used to produce high quality asphalt from residue fractions that are not viscous enough to be employed as asphalt. The composition of the solvent will depend on the character of the starting material and the desired characteristics of the product. An asphalt that is almost adequate and requires only small improvement in viscosity-temperature characteristics may be treated with a solvent containing more acetone and less hydrocarbon. for example, a solvent containing volume acetone and 5% volume toluene. A soft residue requiring both hardening and improved viscosity-temperature characteristics on the other hand will be treated with a solvent containing more hydrocarbon and less acetone, for example, a solvent containing 45% volume toluene and 55% volume acetone.

The low-boiling liquid hydrocarbon should contain fewer than 10 carbon atoms per molecule and typically is heptane, octane, xylene, toluene, benzene, and mixtures thereof. The criteria for selecting the liquid hydrocarbon portion ofthe solvent are that it must be capable of dissolving the asphalt material entirely if used alone in sufficient quantity, it must be easily separated from the extract phase, and, of course, it should be a material that is abundantly available and not too expensive.

The following examples are provided to illustrate the invention by demonstrating improvements effected on specific asphaltic materials using specific solvents.

The examples demonstrate the process of this invention with two different charge stocks. The charge stock shown as A is an asphalt fraction obtained as the residue from a lube oil distillation unit. The material shown as B is the product from processing charge stock A at the conditions shown. The charge stock shown as C is a straight run residue from an atmospheric distillation column that is used to separate crude oil into various components. This material is not an asphalt because it is too soft. In fact, it is too soft to have a penetration test successfully performed. The material shown as D is the product resulting from the treatment of charge stock C at the conditions shown.

The penetrations reported in the table are measured at 77F and are in terms of decimillimeters of penetration by a standard needle under standardized conditions. The viscosities reported in the table are measured at 275F and are in terms of centistokes. The slopes of the viscosity vs. temperature curves reported in the table are the slopes of curves plotting log log viscosity vs. log temperature and are taken between I40F and 275F.

As can be seen from the table, two quite different charge stocks were treated in accordance with this invention to improve greatly the temperature-viscosity characteristics as well as to increase the viscosity. Particularly in regard to the viscosity, it should be brought out that the absolute viscosity of the products B and D are not determining factors of usefulness because the viscosity of a final asphalt product can be varied by such means as .introducing a suitable cutter stock to soften the asphalt or by air blowing or further extraction to harden it after the temperature-viscosity characteristics have been established. Any extraction with the solvent of the present invention will improve the viscosity-temperature characteristics of the lower layer for use as an asphalt. However, other characteristics of the asphalt may also be changed by varying the acetone 3 4 to liquid hydrocarbon ratio of the solvent, by varying l. A process for producing an asphalt with improved the ratio of solvent to asphalt-containing material durviscosity-temperature characteristics which comprises: ing the treatment, by varying the temperature at which a. treating an asphalt residue fraction of a petroleum the extraction process takes place, and by varying the crude oil with a solvent comprising: character of the liquid hydrocarbon portion of the sol- 5 1, at least 1% volume ofa low boiling liquid hydrovent. In general, deeper extractions will produce carbon having less than carbon atoms per harder, more viscous products with flatter viscosity vs. l l d temperature curves. i i 2. at least 50% volume of acetone,

A B c o Penetration 30 l3 90 Viscosity 314 1064 58.5 320 Slope. Temperature vs. Viscosity 4 3.74 3.87 3.53 Extraction Conditions Acetone/Toluene, vol. ratio 80/20 9l/9 Solvent/Residue, wt. ratio 3.2/1 S/l Temperature. C 25 25 The extraction may be effected in any conventional b. separating an upper phase, and manner but it preferably is effected continuously and c. recovering an asphalt with improved viscosity-. countercurrently in multiple stages. Although different temperature characteristics from the lower phase. ratios of acetone to hydrocarbon in the solvent, differ- 2. The process of claim 1 wherein said liquid hydroent ratios of solvent volume to asphalt-containing macarbon comprises toluene. terial volume, different temperatures and different pro- 3. The process of claim 1 wherein said liquid hydrocessing techniques may cause the properties of the carbon comprises heptane. product to change, improvement in the temperature- 4. The process of claim 1 wherein the ratio of the volviscosity characteristics of the material will be effected ume of solvent to the volume of asphalt residue is at by the above-described treatment. least 1.

What is claimed is: 

1. A PROCESS FOR PRODUCING AN ASPHALIT WITH IMPROVED VISCOSITY-TEMPERATURE CHARACTERISTICS WHICH COMPRISES: A. TREATING AN ASPHALT RESIDUE FRACTION OF A PETROLEUM CRUDE OIL WITH A SOLVENT COMPRISING:
 1. AT LEAST 1% VOLUME OF A LOW BOILING LIQUID HYDROCARBON HAVING LESS THAN 10 CARBON ATOMS PER MOLECULE, AND
 2. AT LEAST 50% VOLUME OF ACETONE, B. SEPARATING AN UPPER PHASE, AND C. RECOVERING AN ASPHALT WITH IMPROVED VISCOSITYTEMPERATURE CHARACTERISTICS FROM THE LOER PHASE.
 2. at least 50% volume of acetone, b. separating an upper phase, and c. recovering an asphalt with improved viscosity-temperature characteristics from the lower phase.
 2. The process of claim 1 wherein said liquid hydrocarbon comprises toluene.
 3. The process of claim 1 wherein said liquid hydrocarbon comprises heptane.
 4. The process of claim 1 wherein the ratio of the volume of solvent to the volume of asphalt residue is at least
 1. 